var chooses = document.querySelectorAll('.nav-c');
var nav_bs = document.querySelectorAll('.nav-b');
for (var i = 0; i < chooses.length; i++) {
    chooses[i].index = i;

    chooses[i].onmouseenter = function () {
        for (var i = 0; i < chooses.length; i++) {
            nav_bs[i].style.display = "none";
        }


        nav_bs[this.index].style.display = "block"

    }
    chooses[i].onmouseleave = function () {
        nav_bs[this.index].style.display = "none";
    }


}

